No one ever said drinking whisky would be easy. Forget about how challenging Laphroaig is to drink. It’s hard enough just spelling and pronouncing it!
Well, at least we don’t have to be experts on wine too—or do we? We now have whiskies like Glenmorangie Fino Sherry Finish, Glenmorangie Claret Finish, Balvenie Port Wood Finish, Glenfiddich Solera Reserve, and Talisker finished in Amoroso casks. And I know of at least two whiskies matured in Pedro Ximinez casks.
Pedro Ximinez? I thought he played first base for the Yankees!
As the whisky industry continues to mature, each company hopes to emerge with a new idea that will spark a trend and boost sales. Although finishing off a whisky in a Pedro Ximinez sherry cask might be new, the concept of maturing whisky in used wine casks—particularly sherry wine—is not new at all. Sherry was shipped from Spain to Britain in wooden casks for hundreds of years, and it didn’t take long for the Scotch whisky industry to figure out what to do with the casks after they were emptied.
But which casks are used for maturing whisky? And why? What happens to the sherry casks before they are shipped to Scotland? And what impact does sherry cask aging have on the overall quality of a given whisky?
I decided it would be easier to appreciate the contribution sherry wood has on a given whisky if I had a better understanding of how sherry is made and what makes one sherry variety different from another. With this goal in mind, I packed my bags for Jerez, Spain. Jerez (pronounced “hair-eth”) is a small town in southern Spain, located in the heart of the sherry producing region.
I was honored to have with me the person who probably has the most at stake when it comes to sherry cask aging—David Robertson, the Distillery Manager for The Macallan. After all, Macallan is the only distillery that ages their entire line of single malts exclusively in sherry casks. According to David, more than half of the sherry casks shipped to Scotland for whisky maturation are filled with The Macallan. This year at the Macallan distillery, 12,000 sherry casks will be filled with new make spirit. At any given time, there are more than 20,000 casks filled with sherry in and around Jerez that will ultimately be used to mature The Macallan.
From the grapevine
It’s early September in Jerez. The temperature is in the mid 90s—in the shade! In the middle of the afternoon, there’s no escape from the blazing sunshine. “Time for a quiet, relaxing siesta,” you might think.
Well, think again. For the next two weeks this sleepy town and its neighboring Andalucian countryside will be working dawn to dusk harvesting grapes to make sherry—something for which all of us who enjoy whisky aged in sherry casks can be grateful.
At the Tevasa Cooperage they can’t make the casks fast enough. The incessant sawing of the staves and hammering of metal barrel rings creates a clatter so loud, there’s no way anyone within a mile of the cooperage could even entertain the thought of a siesta. With enough wooden staves there to make more than 10,000 casks, I don’t expect they’ll be stopping production anytime soon.
Over at the El Agostado Vineyard and many others like it, ripe Palomino grapes—known for making the highest quality dry sherry—droop heavily from the vines that thrive in chalky white soil known as albariza. When it rains, the soil readily absorbs the moisture. In the summer, the surface of the soil bakes and hardens, preventing the moisture in the soil from escaping. Its light color reflects the sun’s bright rays. Workers harvest the grapes quickly and carefully, placing them into crates, which are then transported to processing facilities.
Some grape processing facilities are small, others are very large and industrial looking. One of these facilities is the Les Copas de Gonzales Byass Bodega (where Teo Pepe sherry is produced). This particular harvesting facility is so massive that dozens of trucks continually unload crates of grapes. The grapes are crushed and pressed to release the mosto (grape juice), which is then transferred to the adjacent bodega (a tall, well-aired warehouse for storing sherry) while it matures.
Within the bodega, the mosto is fermented in tall cylindrical stainless steel tanks and becomes wine, ultimately being transferred into one of 40,000 wooden casks sheltered inside the bodega. Here the wine continues to ferment. It is ultimately fortified with grape spirit (to approximately 15% alcohol when producing the lighter fino sherries, and to approximately 17-18% when producing oloroso sherries).
The level of alcohol is critical. At 15%, a velo de flor (literally “flowered veil”)—a natural yeast that thrives in the Jerez air—is allowed to grow on the surface of the wine inhibiting oxidation of the sherry. For this reason, the lighter fino sherries express a fresh, tangy, yeasty character. With the oloroso sherries, the alcohol level kills off the flor, exposing the sherry to air. This oxidation produces a darker color and more nutty flavor in olorosos. Generally speaking, the best wines are selected for finos, because they are so light and delicate.
The wines mature into full-fledged sherry via the solera aging system. Each solera consists of a series of wooden casks (called butts) containing sherry, usually placed in rows according to age. Traditionally, the most mature wines are in butts on the bottom row. Younger wines of different levels of maturation sit in rows of butts above them, with the youngest wines traditionally on the top row. The entire series of rows is called a criadera. Wine for bottling is taken from the bottom row of butts, with only a fraction of the butt being emptied. These butts are topped up with wines from the rows of butts above them, all the way up the criadera, until the youngest wines are introduced into the system. The solera system ensures a mature, consistent product.
Show and smell
Even with all these Spanish oak sherry casks being shipped to Scotland, the predominant cask that is used to mature whisky is American oak casks that previously contained bourbon. “A Spanish oak cask is ten times more expensive than an American oak cask,” David pointed out. “And this is only one part of the cost associated with the commitment of using sherry casks exclusively.” Another big cost is research. David explained that since the majority of the wood used to age whisky is American oak, that is where most of the organized research is focused.
Because of this, Macallan has decided to conduct their own research on Spanish oak. “Bourbon casks are more tightly controlled and more consistent in quality,” notes David. “Sherry casks have a greater potential for complexity—there are dozens of different types of sherries and the potential for The Macallan is equally as great—but the casks also have been more variable. We want to minimize this variability to ensure a more consistent product.”
He continued. “Right now, before we put whisky in a sherry cask, we just smell the cask to judge its quality. What we really want to do is be more scientific in our approach when determining the wood quality of a cask before we age whisky in it for many years. Our goal is to be able to scrape a wood sample from a cask and analyze it in a laboratory for key components to determine its overall quality so we can know which casks will produce a good whisky and which ones won’t. Right now it’s too much hit or miss.”
To this end, he has commissioned a series of studies to be done by wood expert Jim Swan of the consulting firm Tatlock and Thomson. Some of the preliminary studies have proved promising.
In one study, David selected samples from dozens of different Macallan casks of varying ages, nosed them, and assigned a quality rating to each one. The same cask samples were then sent to Tatlock and Thomson where they were analyzed for specific wood and wine extracts to determine if there was a correlation between the quality of the whisky and the levels of wood or wine extracts in the whisky.
The results were conclusive in many respects. As it is widely believed in the whisky industry, the study suggests that the quality of the whisky is highly correlated with the type and quality of the wood it is aged in. More specifically, the tests show a strong correlation between the quality of the whisky and specific wood extractives, namely vanillin (a wood lignin extractive) and ellagic acid (a wood breakdown product). These preliminary studies seem to suggest that wood extractives like vanillin and ellagic acid might be used as “markers” when developing an analytical test on Spanish oak wood samples to determine whether a specific cask should be used for whisky maturation.
Another finding from these studies addresses the impact of the sherry wine on the quality of the whisky. One might think that its impact on The Macallan whisky would be strikingly significant, given that all of The Macallan whisky is aged exclusively in sherry oak. While the studies by Tatlock and Thomson suggest a good correlation, it is not nearly as strong as the type and quality of the wood itself.
“When using Spanish oak, the studies indicate that about 10% of the quality of The Macallan whisky is based on the sherry wine-derived compounds,” notes David. “In fact, we have some casks of Macallan whisky from the late 1970s aged in different sherries—fino, amontillado, and oloroso—and we’re seeing little difference between them. The wine’s impact would be more significant if American oak casks were used.”
While the initial studies have shown the quality of The Macallan whisky is largely “wood driven” and that the impact of sherry wine extractives are lesser so, there are still many other variables which David hopes to isolate and quantify. These variables include the impact of oxidation on The Macallan and the overall contributions of the new make spirit to the quality of the whisky.
One thing is for sure. The impact that sherry bodegas have on the whisky industry is enormous and will continue to be so. To quote David Robertson, “without the sherry casks and Spanish oak, it just wouldn’t be The Macallan.”